Immunoassays have been used routinely for the identification and quantitation of haptens, antigens and antibodies (all broadly termed analytes). The basic principle of all immunoassays is predicated on the specific binding between components of a reaction pair (e.g. antigen/antibody, hapten/antibody, etc.) where, in some cases, one component is labeled in such a fashion as to be easily analyzed by some external means.
Radioimmunoassay (RIA) is based on the use of a radioisotope as a label for one of the components of a specific binding pair. A radioisotopically labeled component can then be detected by counting the radiation emitted by the isotope using a suitable instrument.
Other methods of labeling one component of a specific binding pair have been developed. The use of enzyme and fluorescent labels have recently been employed and are termed enzyme immunoassay (EIA) and fluorescent immunoassay (FIA) respectively. Again, with the use of suitable reagents and instruments, these labels can be used for the determination of analytes in a liquid medium. Many variations to the basic procedures are in use, but most require the steps of reaction, separation, and detection of label.
More recently, electrochemical sensors have been employed in an effort to simplify and/or improve the sensitivity of these procedures. Basically, they employ an ion selective electrode to detect the reaction product of an enzyme which has been used as a label for one component of a specific binding pair.
The present invention seeks to eliminate the preparation of a labeled component of a specific binding pair, the separation of such a component from the assay system, as well as its subsequent detection; thereby greatly simplifying the method of performing an immunoassay. More specifically, the present invention relates to a new and useful improvement in a method for the determination of analytes in a liquid medium by the use of a biochemically sensitive semiconductor device set forth in the following description and specifications.